(a) Field of the Invention
The present invention relates to a six-speed powertrain of an automatic transmission of a vehicle installed in an automatic transmission and realizing six forward speeds and one reverse speed.
(b) Description of the Related Art
A multi-stage gearshift mechanism of an automatic transmission includes a plurality of planetary gear sets. A powertrain having such a plurality of planetary gears sets varies the torque in multi-stages and outputs it to an output shaft when receiving a converted engine torque from a torque converter.
The more speeds the powertrain of an automatic transmission has, the better the power performance and fuel consumption are. Therefore, it is desirable for powertrains to have as many speeds as possible.
Even for the same number of speeds, durability, power transmission efficiency, and size/weight of a transmission are substantially dependent on how planetary gear sets are arranged. Therefore, research for more structural strength, less power loss, and more compact packaging are continuously being conducted.
Usually, development of a powertrain using planetary gear sets does not devise a wholly new type of planetary gear set. To the contrary, it invokes how single/double pinion planetary gear sets are combined, and how clutches, brakes, and one-way clutches are disposed to the combination of Ravingneaux planetary gear sets such that required shift speeds and speed ratios are realized with minimal power loss.
For a manual transmission, too many speeds cause a driver the inconvenience of excessive manual shifting. However, for an automatic transmission, a transmission control unit automatically executes shifting by controlling the operation of the powertrain, and therefore, more speeds usually implies more merits.
Accordingly, research of four-speed and five-speed powertrains has been undertaken, and recently, a powertrain of an automatic transmission enabling six forward speeds and one reverse speed has been developed. However, current six-speed transmissions have a number of drawbacks including excessive size and weight and low durability.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.